94 pickup will not warm up

[Derick195]

I got a 94 Nissan pick up truck that will not warm up unless idling, one day I was driving and the cause just gradually went down and will not warm up unless sitting and idling I have changed the thermostat and water pump took the fan clutch off and put a electric fan on it with the thermostatic switch I don't know what else to do but IT IS NOT THE GAUGE any ideas?

[whomadewho]

Check the radiator cap

[Derick195]

Check the radiator cap

Just put one on it with the new radiator, all I can even think is that it's bypassing somewhere

[whomadewho]

Recheck the part # l am not sure if it will effect the performance: - 1986.5 -1994 & 1995 - 1997 use different thermostats. Something you could try - find someone with a infered therometer and check temp. After driving. Something also possible, l know you just replaced the thermostat, but it is possible you got a bad one. Just my opinion, I would only use a OEM Nissan thermostat. Quick question - What temp. Thermostat did you use...

[Rev_D21]

My question: Is the truck not warming up or is the gauge reading incorrectly?

[Derick195]

Like I said the gauge works right, I put that electric fan with the tempature switch on it set for 170 and while idleing it will warm up to half way on the gauge and the fan will kick on, the thermostat in the truck now came from Nissan but the motor has been swapped so there could be a chance that it's a 95 up motor I mean honest opinion is that it's bypassing the thermostat I don't know if it's the wrong one or if it's stuck open or what but it's driving me insane haha

[whomadewho]

A couple of things you can try - replace the radiator cap with a higher pressure cap,this will increase the pressure in the cooling system,which will increase the temp. You can also remove the thermostat,place it in a pan with water and heat it up and see if the thermostat is working. Easier solution place a thermometer in the radiator to see at what temp. the thermostat is opening at.
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[whomadewho]

Quick question - How thick,how many rows,& what is the flow direction?? It's possible the radiator to big for the vehicle.

[Derick195]

I am currently at work but the water is constantly circulating threw the radiator as if the thermostat was open, I have bout one from autozone, Oriellys, advanced,napa, a engine shop called performance masters, and the last one come straight from Nissan I'm literally mind f*** on how the water is constantly circulating

[whomadewho]

If the coolant is constantly circulating,this would indicate that the thermostat is stuck open. Look around and see if you can find a 195 degree Superstant thermostat. Again there is a difference in the engine years,so you are going to have to figure what year you are dealing with..

[Derick195]

Little update on it I read somewhere that there was a bleeder for the coolant so I bled it out and while I was you could see the coolant circulating and stopping while the thermostat was opening and closing so I beliebe the thermostat is working correctly, I also found out from my buddy who had done the motor swap that it is a 91 model motor, I checked at the parts stores and everything on the 91 and 94 model motors are the same as far as the water pump, thermostat, and radiator but even after bleeding the system it is still no better, it warms up a bit faster at idle but still cools right down after going half a mile down the road there is got to be somthing that I am missing here

[Sharp]

Hi, I cant see if anyone suggested you check the hose temperatures going to and from the heater core. What usually happens when a heater core goes bad is that it will drip, but it will sometime just not allow the water to circulate through if clogged. If both lines are hot to the touch after the truck is warmed up, then you can move on.

The other thing I would ask is what is your dash temperature reading? Does your truck run about half way on the temperature when sitting but then drop when you start driving down the road or get up to speed?

I had an issue with my truck not putting out a lot of heat in the winter, barely enough to defrost the wind screen, but I placed a cardboard box (flattened) in front of the radiator to block the wind flow and it work much better. Eventually I found that my thermostat was working very hard. As it is prelubed from the factory I opted to just replace it, and it worked fine after that. If your truck has been sitting a long time. Drain all the radiator coolant and replace it with a proper mix. There is lubricant in the coolant and it is designed to keep the thermostat to function properly. Hope this helps.